Table 2.

Ficat and arlet classification system

Stage	Features
0	Normal radiographs (silent hip)
I	Slight abnormality as patchy/opaque areas, minor osteopenia
II	Sclerotic or cystic lesions
	IIa: No crescent sign
	IIb: Crescent sign without flattening of the femoral head
III	Flattening of the femoral head or femoral head collapse
IV	Femoral head collapse and osteoarthritis of the hip (joint space narrowing, osteophytes and acetabular changes)